1. Field of the Invention
The invention relates to a device for fastening a support for on-board equipment in an aircraft enabling a precise positioning of the support with respect to the aircraft.
An aircraft comprises a large number of pieces of equipment generally fixed individually and in a removable or interchangeable way to enable especially the dismounting and quick replacement of a malfunctioning piece of equipment.
The structure of the aircraft may be provided with fastening or hooking lugs to which the equipment is for example screwed. The dimensions of the fastening lugs and of a piece of equipment correspond to each other within the limits of the manufacturing tolerances of the aircraft on the one hand and of the equipment on the other hand.
However, the manufacturing tolerances may be far too great for certain pieces of equipment such as an inertial guidance unit or a head-up display system whose use requires very precise positioning with respect to the entire structure of the aircraft.
A head-up display system, also known as a head-up collimator, enables the pilot to be provided with collimated information superimposed on his distant field of view.
A collimator has a projector, generally placed above the pilot's head, and a semi-transparent mirror placed before his eyes. The projector sends a collimated light beam containing information to the mirror. The mirror is transparent to the light rays sent by the scene and reflects the rays, coming from the projector, to the pilot's eyes. Thus, the pilot can read the information while at the same time observing the scene.
A head-up collimator is used in civil aviation for landing. It enables the display of an image of the landing strip that is in accordance with the real terrain. The only way to superimpose the image on the scene without having a disturbing offset is to position the collimator very precisely in relation to the geometrical references of the structure of the aircraft.
2. Description of the Prior Art
This positioning is achieved during an operation for harmonizing a collimator with a carrier aircraft. For an aircraft, this harmonizing operation consists in mounting it on jacks, placing it horizontally to the ground, defining geometrical references by using optical instruments and adjusting the position of the collimator with respect to these geometrical references by means of a sighting telescope. The geometrical references of the aircraft are generally represented by a target fixed to the ground. A sighting telescope is fixed to the collimator and then the position of the collimator is adjusted until the telescope is trained on the target.
The operation of harmonization ends with the fastening to the aircraft of the collimator in the adjusted position.
The operation for harmonizing a piece of equipment with its aircraft is lengthy, limited by constraints and costly. It is therefore sought to avoid repeating this operation after each dismounting of equipment. The problem is to enable the dismounting and remounting of a piece of equipment on board the aircraft with high precision.
A partial approach consists of the use of an equipment support. The support may be hooked and secured to the support and it can also be dismantled.
The mounting of equipment on the support is reproducible with sufficient precision to remove the need for the operation of harmonizing the aircraft with the equipment and to be able to obtain satisfaction the operation of harmonizing the aircraft with the support. The latter operation is as cumbersome as the former one, but enables the dismounting, replacement and remounting of the equipment while guaranteeing that the equipment will be rightly positioned.
However, during certain operations for the maintenance of the aircraft, it is necessary to dismantle also the support. The problem then is to provide for the precise remounting of the support in avoiding a new operation of harmonization.